Ace inhibitors with a sulfhydryl group (i.e., captopril) stimulate vasodilator prostaglandin (PG) synthesis, whereas non-sulfhydryl ace inhibitors (i.e., enalapril) do not. The hypothesis being tested is whether PG synthesis inhibition by indomethacin can influence the antihypertensive response to 3 different ace inhibitors (captopril, enalapril, and spirapril).